CONFIG_CAVIUM_ERRATUM_27456 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm64

Cavium erratum 27456: Broadcast TLBI instructions may cause icache corruption

configname: CONFIG_CAVIUM_ERRATUM_27456

Linux Kernel Configuration
└─>Kernel Features
└─>ARM errata workarounds via the alternatives framework
└─>Cavium erratum 27456: Broadcast TLBI instructions may cause icache corruption
In linux kernel since version 4.1 (release Date: 2015-06-21)  
On ThunderX T88 pass 1.x through 2.1 parts, broadcast TLBI
instructions may cause the icache to become corrupted if it
contains data for a non-current ASID. The fix is to
invalidate the icache when changing the mm context.

If unsure, say Y.